Low profile electrodes for an angioplasty shock wave catheter

ABSTRACT

Described herein are low-profile electrodes for use with an angioplasty shockwave catheter. A low-profile electrode assembly may have an inner electrode, an insulating layer disposed over the inner electrode such that an opening in the insulating layer is aligned with the inner electrode, and an outer electrode sheath disposed over the insulating layer such that an opening in the outer electrode sheath is coaxially aligned with the opening in the insulating layer. This layered configuration allows for the generation of shockwaves that propagate outward from the side of the catheter. In some variations, the electrode assembly has a second inner electrode, and the insulating layer and outer electrode may each have a second opening that are coaxially aligned with the second inner electrode. An angioplasty shockwave catheter may have a plurality of such low-profile electrode assemblies along its length to break up calcified plaques along a length of a vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/680,033, filed Aug. 6, 2012, which is hereby incorporated byreference in its entirety.

BACKGROUND

Currently, angioplasty balloons are used to open calcified lesions inthe wall of an artery. However, as an angioplasty balloon is inflated toexpand the lesion in the vascular wall, the inflation pressure stores atremendous amount of energy in the balloon until the calcified lesionbreaks or cracks. That stored energy is then released and may stress andinjure the wall of the blood vessel.

Electrohydraulic lithotripsy has been typically used for breakingcalcified deposits or “stones” in the urinary or biliary track. Recentwork by the assignee shows that lithotripsy electrodes may similarly beuseful for breaking calcified plaques in the wall of a vascularstructure. Shockwaves generated by lithotripsy electrodes may be used tocontrollably fracture a calcified lesion to help prevent sudden stressand injury to the vessel or valve wall when it is dilated using aballoon. A method and system for treating stenotic or calcified vesselsis described in co-pending U.S. application Ser. No. 12/482,995, filedJun. 11, 2009. A method and system for treating stenotic or calcifiedaortic valves is described in co-pending U.S. application Ser. No.13/534,658, filed Jun. 27, 2012. As described in those applications, aballoon is placed adjacent leaflets of a valve to be treated and isinflatable with a liquid. Within the balloon is a shock wave generatorthat produces shock waves that propagate through the liquid and impingeupon the valve. The impinging shock waves soften, break and/or loosenthe calcified regions for removal or displacement to open the valve orenlarge the valve opening. Additional improved lithotripsy or shockwaveelectrodes that can readily access and treat various locations in thevasculature for angioplasty and/or valvuloplasty procedures may bedesirable.

BRIEF SUMMARY

Described herein are low-profile electrodes for use with an angioplastyshockwave catheter. A low-profile electrode assembly may have an innerelectrode, an insulating layer disposed over the inner electrode suchthat an opening in the insulating layer is aligned with the innerelectrode, and an outer electrode disposed over the insulating sheathsuch that an opening in the outer electrode is coaxially aligned withthe opening in the insulating layer. This layered configuration allowsfor the generation of shockwaves that initiate and/or propagate outwardfrom a side of the catheter. In some variations, the electrode assemblymay have at least a second inner electrode, and the insulating layer andouter electrode may each have at least a second opening that arecoaxially aligned with the second inner electrode. An angioplastyshockwave catheter may have a plurality of such low-profile electrodeassemblies along its length to break up calcified plaques along a lengthof a vessel.

One variation of a device for generating shockwaves may comprise anaxially extending catheter, a balloon surrounding a portion of thecatheter, said balloon being fillable with a conductive fluid, aninsulating layer wrapped around a portion of the catheter within theballoon, the insulating layer having a first aperture therein, a firstinner electrode carried within the catheter and aligned with the firstaperture of the insulating layer, and an outer electrode mounted on theinsulating layer and having a first aperture coaxially aligned with thefirst aperture in the insulating layer and arranged so that when theballoon is filled with fluid and a voltage is applied across theelectrodes, a first shockwave will be initiated from a first sidelocation of the catheter. The insulating layer may be an insulatingsheath and the outer electrode may be in the form of a sheath that iscircumferentially mounted around the insulating sheath. The size of thefirst aperture in the outer electrode may be larger than the size of thefirst aperture in the insulating sheath. The device may further comprisea first wire and a second wire, where the first and second wires extendalong the length of the catheter, and where the first wire may beconnected to the first inner electrode, and the second wire may beconnected to the outer electrode. In some variations, the catheter mayhave first and second grooves that extend along the length of thecatheter, and the first wire is slidably disposed within the firstgroove and the second wire is slidably disposed within the secondgroove. For example, a length of the first and second wires may bepartially secured within the first and second grooves. The first innerelectrode and the outer electrode may be crimped over an electricallyconductive portion of the first and second wires, respectively. In somevariations, the first inner electrode may be a hypotube that is crimpedover the first wire.

In some variations of a device for generating shockwave, the insulatingsheath may have a second aperture circumferentially opposite the firstaperture in the insulating sheath and the device may further comprise asecond inner electrode aligned with the second aperture in theinsulating sheath and the outer electrode sheath may have a secondaperture coaxially aligned with the second aperture in the insulatingsheath and arranged so that when the balloon is filled with a fluid anda voltage is applied across the second inner electrode and the outerelectrode, a second shockwave will be initiated from a second sidelocation of the catheter that is opposite to the first side location. Insome variations, the device may comprise a first wire, a second wire,and a third wire, where the first, second and third wires that extendalong the length of the catheter, where the first wire is connected tothe first inner electrode, the second wire is connected to the outerelectrode, and the third wire is connected to the second innerelectrode. The catheter may have first, second and third grooves thatextend along the length of the catheter, and the first wire may beslidably disposed within the first groove, the second wire may beslidably disposed within the second groove, and the third wire may beslidably disposed within the third groove. The first inner electrode andthe second inner electrode may be crimped over an electricallyconductive portion of the first and third wires, respectively. The firstinner electrode and the second inner electrode may be first and secondhypotubes that are each crimped over the first and third wires,respectively. In some variations, the surface of the first and secondcrimped hypotubes each circumferentially spans a portion of the elongatemember. For example, the first and second crimped hypotubes may eachcircumferentially span at least ⅙ of the way around the circumference ofthe elongate member.

Optionally, the insulating sheath may have a third aperturecircumferentially 90 degrees from the first aperture in the insulatingsheath and may further comprise a third inner electrode aligned with thethird aperture in the insulating sheath. The outer electrode sheath mayhave a third aperture coaxially aligned with the third aperture in theinsulating sheath and arranged so that when the balloon is filled with afluid and a voltage is applied across the third inner electrode and theouter electrode, a third shockwave will be initiated from a third sidelocation that is 90 degrees offset from the first side location. In somevariations, the insulating sheath may have a fourth aperturecircumferentially opposite the third aperture in the insulating sheathand the device may further comprise a fourth inner electrode alignedwith the fourth aperture in the insulating sheath. The outer electrodesheath may have a fourth aperture coaxially aligned with the fourthaperture in the insulating sheath and arranged so that when the balloonis filled with a fluid and a voltage is applied across the fourth innerelectrode and the outer electrode, a fourth shockwave will be initiatedfrom a fourth side location that is opposite to the third side location.

Another variation of a device for generating shockwaves may comprise anaxially extending catheter, a balloon surrounding a portion of thecatheter, the balloon being fillable with a conductive fluid, a firstinner electrode mounted on the side of the catheter, an insulating layerhaving an aperture disposed over the first inner electrode such that theaperture is coaxially aligned with the first inner electrode, and anouter electrode having an aperture disposed over insulating layer suchthat the outer electrode aperture is coaxially aligned with theinsulating layer aperture. In some variations, the first innerelectrode, insulating layer and outer electrode do not protrude morethan 0.015 inch from the outer surface of the catheter. The device mayfurther comprise a second inner electrode mounted on the side of thecatheter at a location that is circumferentially opposite to the firstinner electrode, where the insulating layer may have a second aperturecoaxially aligned with the second inner electrode and the outerelectrode may have a second aperture that is coaxially aligned with thesecond aperture of the insulating layer.

One variation of a system for generating shockwaves may comprise anaxially extending catheter, a balloon surrounding a portion of thecatheter, the balloon being fillable with a conductive fluid, a firstelectrode assembly at a first location along the length of the catheter,the first electrode assembly comprising a first inner electrode, asecond inner electrode, and an outer electrode and configured toinitiate shockwaves at two circumferentially opposite locations, asecond electrode assembly at a second location along the length of thecatheter, the second electrode assembly comprising a first innerelectrode, a second inner electrode, and an outer electrode andconfigured to initiate shockwaves at two circumferentially oppositelocations, a third electrode assembly at a third location along thelength of the catheter, the third electrode assembly comprising a firstinner electrode, a second inner electrode, and an outer electrode andconfigured to initiate shockwaves at two circumferentially oppositelocations, a fourth electrode assembly at a fourth location along thelength of the catheter, the fourth electrode assembly comprising a firstinner electrode, a second inner electrode, and an outer electrode andconfigured to initiate shockwaves at two circumferentially oppositelocations, a fifth electrode assembly at a fifth location along thelength of the catheter, the fifth electrode assembly comprising a firstinner electrode, a second inner electrode, and an outer electrode andconfigured to initiate shockwaves at two circumferentially oppositelocations, and a voltage pulse generator, where the channels of thevoltage pulse generator are connected to one or more of the electrodeassemblies. In some variations, the first inner electrode of the firstelectrode assembly may be connected is a first output of the voltagepulse generator, the second inner electrode of the first electrodeassembly may be connected to the first inner electrode of the secondelectrode assembly, the first inner electrode of the third electrodeassembly may be connected to a second output of the voltage pulsegenerator, the second inner electrode of the third electrode assemblymay be connected to a third output of the voltage pulse generator, thefirst inner electrode of the fourth electrode assembly may be connectedto a fourth output of the voltage pulse generator, the second innerelectrode of the fourth electrode assembly may be connected to the firstinner electrode of the fifth electrode assembly, and the second innerelectrode of the second electrode assembly, the outer electrode of thethird electrode assembly, and the second inner electrode of the fifthelectrode assembly may all be connected to a fifth output of the voltagepulse generator.

Another variation of a device for generating shockwaves may comprise anelongate member, a first electrode assembly located along the side ofthe elongate member at a first longitudinal location, where the firstelectrode assembly is configured to initiate shockwaves at a first sidelocation on the elongate member, a second electrode assemblycircumferentially opposite the first electrode assembly, where thesecond electrode assembly is configured to initiate shockwaves at asecond side location that is circumferentially opposite the first sidelocation of the elongate member, and a balloon surrounding a portion ofthe elongate member, the balloon being fillable with a conductive fluid.

Another variation of a system for generating shockwaves may comprise ahigh voltage pulse generator having a plurality of high voltage outputchannels, a catheter, a plurality of shockwave sources located along alength of the catheter, where the number of high voltage output channelsdriving the plurality of shockwave sources is less than the number ofshockwave sources, and a balloon surrounding the length of the catheterthat has the shockwave sources, the balloon being fillable with aconductive fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a shockwave angioplasty device developed by the assignee.

FIG. 2 is a cross-sectional view of a low-profile electrode.

FIGS. 3A-3E schematically depicts the assembly of another variation of alow-profile electrode.

FIG. 4 depicts one variation of a shockwave angioplasty device.

FIG. 5A depicts another variation of a shockwave angioplasty device.FIGS. 5B and 5C are perspective views of a plurality of low-profileshockwave electrode assemblies that may be used in a shockwaveangioplasty device. FIGS. 5D and 5E are perspective and side views of aproximal hub of a shockwave angioplasty device. FIG. 5F is a side viewof a high-voltage connector of a shockwave angioplasty device.

FIG. 6A depicts a top view of one variation of a low-profile shockwaveelectrode assembly and one variation of an inner electrode. FIGS. 6B and6C depict various views of one variation of an outer electrode sheath ofa shockwave electrode assembly. FIG. 6D depicts one variation of aninsulating sheath of a shockwave electrode assembly. FIGS. 6E-6G depictother variations of an outer electrode sheath and insulating sheath.FIG. 6H depicts another variation of an inner electrode of a shockwaveelectrode assembly.

FIGS. 7A-7D depict one method of assembling a low-profile shockwaveelectrode assembly.

FIG. 8A depicts a side view of a catheter of a shockwave device. FIG. 8Bis a cross-sectional view of the catheter of FIG. 8A.

FIG. 9 is a cross-sectional view depicting the connectivity between agrooved wire and an outer electrode sheath of a shockwave electrodeassembly.

FIG. 10A schematically depicts a shockwave electrode assembly having twoinner electrodes that are in a direct connect configuration. FIGS.10B-10D depict the connectivity between the inner electrodes and outerelectrodes to attain the configuration of FIG. 10A.

FIG. 11A schematically depicts a shockwave electrode assembly configuredin series. FIGS. 11B-11D depict the connectivity between the innerelectrodes and outer electrodes to attain the configuration of FIG. 11A.

FIG. 12A schematically depicts two shockwave electrode assemblies thatare in a direct connect configuration. FIGS. 12B and 12C depict theconnectivity between the inner electrodes and outer electrodes to attainthe configuration of FIG. 12A.

FIG. 13A schematically depicts two shockwave electrode assembliesconfigured in series. FIGS. 13B-13D depict the connectivity between theinner electrodes and outer electrodes to attain the configuration ofFIG. 13A.

FIG. 14A schematically depicts the connectivity of five shockwaveelectrode assemblies. FIGS. 14B-14G depict the connectivity between theinner electrodes and outer electrodes and intermediate nodes (e.g., adistal marker band) to attain the configuration of FIG. 14A.

DETAILED DESCRIPTION

Described herein are devices and systems that comprise one or morelow-profile lithotripsy or shockwave electrodes that may be suitable foruse in angioplasty and/or valvuloplasty procedures. Lithotripsy orshockwave electrodes may be sealed within an angioplasty orvalvuloplasty balloon that is inflated with a fluid (e.g., saline and/orimaging contrast agent). A shockwave electrode may be attached to asource of high voltage pulses, ranging from 100 to 10,000 volts forvarious pulse durations. This may generate a gas bubble at the surfaceof the electrode causing a plasma arc of electric current to traversethe bubble and create a rapidly expanding and collapsing bubble, whichin turn creates a mechanical shockwave in the balloon. Shockwaves may bemechanically conducted through the fluid and through the balloon toapply mechanical force or pressure to break apart any calcified plaqueson, or in, the vasculature walls. The size, rate of expansion andcollapse of the bubble (and therefore, the magnitude, duration, anddistribution of the mechanical force) may vary based on the magnitudeand duration of the voltage pulse, as well as the distance between ashockwave electrode and the return electrode. Shockwave electrodes maybe made of materials that can withstand high voltage levels and intensemechanical forces (e.g., about 1000-2000 psi or 20-200 ATM in a fewmicroseconds) that are generated during use. For example, shockwaveelectrodes may be made of stainless steel, tungsten, nickel, iron,steel, and the like.

Traditional coaxial shockwave electrodes may be suitable for use in anangioplasty or valvuloplasty balloon, however, when paired inconjunction with a catheter having a guide wire lumen, the crossingprofile (i.e., cross-sectional area) may be too large to navigatethrough and access certain regions of the vasculature. FIG. 1 depictingan example of a shockwave assembly 100 comprising a balloon 106, acoaxial electrode 102 attached in parallel with a catheter 104. Forexample, a coaxial electrode 102 may have a cross-sectional diameter ofabout 0.025 inch to about 0.065 inch, and a catheter 104 may have across-sectional diameter of about 0.035 inch, which would result in theassembly 100 having a total cross-sectional diameter of at least about0.06 inch. Such a large crossing profile may limit the ability of theshockwave system to treat tortuous vascular areas and also limit thenumber of patients that may be treated. Described herein are low-profileshockwave electrodes that may be located along the outer surface of anelongate member (such as a catheter having a guide wire lumen) that donot protrude more than 0.015 inch from the outer surface of the elongatemember. For example, the low-profile shockwave electrodes describedbelow may increase the crossing-profile of the elongate member by onlyabout 0.005 inch to about 0.015 inch, thereby minimally affecting theability of the elongate member to access and treat target vasculartissue.

Also described herein are shockwave devices with a plurality ofelectrodes along the side of an elongate member that are sealablyenclosed in a balloon (i.e., sealed in an enclosed balloon). Since themagnitude, duration and distribution of the mechanical force impingingon a portion of tissue depends at least in part on the location anddistance between the shockwave source and the tissue portion, ashockwave device having multiple shockwave electrodes at variouslocations along the length of the elongate member may help to provideconsistent or uniform mechanical force to a region of tissue. Theplurality of electrodes may be distributed across the device (e.g.,along a longitudinal length of the elongate member) to minimize thedistance between the shockwave source(s) and the tissue location beingtreated. For example, a calcified region of a vein or artery may extendover some longitudinal distance of the vein or artery, and a pointsource shockwave electrode would not be effective across the full extentof the calcified region because of the varying distance from theshockwave source to the various portions of the calcified region.Described herein are shockwave devices that comprise a plurality oflow-profile shockwave electrodes located along a longitudinal length ofan elongate member to distribute shockwaves across a length of calcifiedplaque. The low-profile shockwave electrodes may be located along thecircumference of an elongate member. The elongate member may also besized and shaped to distribute shockwave forces to a non-linearanatomical region. For example, the elongate member may be curved,having a radius of curvature that approximates the radius of curvatureof a valve (e.g., an aortic valve). A shockwave device with a curvedelongate member may be suitable for applying shockwaves to breakcalcified plaques in the vicinity of a valve and/or valve leaflets aspart of a valvuloplasty procedure.

One variation of a low-profile shockwave electrode assembly may comprisea first electrode, a second electrode stacked over the first electrode,and an insulating layer between them. Stacking the second electrode overthe first electrode may form a layered electrode assembly that may beformed on the side of a catheter without substantially increasing thecross-sectional profile of the catheter. A stacked or layered electrodeassembly located on the side of a catheter may also be able to generateshockwaves that propagate from the side of the catheter withoutperpendicularly protruding from the catheter (which would increase thecross-sectional profile of the catheter). The insulating layer may havea first opening and the second electrode may have a second opening thatis coaxially aligned with the first opening. Coaxial alignment betweenthe first opening in the insulating layer and the second opening in thesecond electrode may comprise aligning the center of each of theopenings along the same axis. The opening in the insulating layer andthe opening in the second electrode may be concentric, such that thecenter of the insulating layer opening is aligned with the center of thesecond electrode opening. In some variations, a shockwave device maycomprise an elongate member (such as a catheter) and a shockwaveelectrode assembly having a first electrode that is substantiallyco-planar with the outer surface of the elongate member. For example,the first electrode may be a pronged electrode that is inserted into theelongate member and connected to a high voltage source via wires withinthe elongate member. Alternatively, the first electrode may be ahypotube crimped to an electrically conductive portion of a wire, wherethe wire is located within a longitudinal channel or groove of theelongate member. The wire may have one or more electrically insulatedportions and one or more electrically conductive portions, where theconductive portions may align with a first opening of the insulatinglayer and a second opening of the second electrode. The insulating layermay be a sheet or sheath that wraps at least partially around thecircumference of the elongate member and overlaps the first electrode.The insulating layer may overlap the first electrode such that the firstelectrode is electrically isolated from the environment external to theelongate member but for the opening in the insulating layer. The secondelectrode may be a ring, sheet, or sheath having a second opening thatstacks and/or overlaps with the insulating layer such that the secondopening is coaxially aligned with the first opening of the insulatinglayer. The second electrode may be circumferentially wrapped over theinsulating layer. Stacking the first electrode, insulating layer, andsecond electrode along the outer surface of the elongate member mayallow for a shockwave electrode assembly to have a low profile withrespect to the elongate member, and coaxially aligning the opening ofthe insulating layer with the opening of the second electrode may allowfor the generation of shockwaves that propagate from the side of theelongate member.

One example of a low-profile shockwave electrode assembly is depicted inFIG. 2. FIG. 2 depicts a cut away perspective view of a low-profilecoaxial shockwave electrode assembly 200 that may be located on anelongate member 20 (e.g., a catheter) and enclosed in a balloon (e.g.,an angioplasty or valvuloplasty balloon). The electrode assembly 200 maycomprise a first electrode 1, an insulating layer 2 overlaying the firstelectrode, and a second electrode 3. The first electrode 1 may be apositive electrode and the second electrode 3 may be a negativeelectrode (or vice versa). The elongate member 20 may have a guide wirelumen extending along a length of its longitudinal axis. The firstelectrode 1 may have a thickness from about 0.001 inch to about 0.01inch, e.g., 0.002 inch, and may be attached along the outer surface ofthe elongate member 20. The insulating layer 2 may be made of anymaterial with a high breakdown voltage, such as Kapton, ceramic,polyimide or Teflon. The insulating layer 2 may be about 0.001 inch toabout 0.006 inch, e.g., 0.0015 inch, 0.0025 inch, and may have anopening 7 that is aligned over the first electrode 1. Although thesecond electrode 3 is depicted as having a ring shape, it should beunderstood that the second electrode may be a planar sheet or layer. Thesecond electrode 3 may have a central opening 8 and stacked over theinsulating layer 2 such that the second electrode opening 8 is coaxiallyaligned with the insulating layer opening 7. The openings 7, 8 may be inthe shape of a circle, oval, ellipse, rectangular, or any desired shape.The second electrode 3 may have a thickness from about 0.001 inch toabout 0.015 inch, e.g., 0.0025 inch, 0.004 inch. The total thickness ofthe shockwave electrode assembly 200 may be from about 0.002 inch toabout 0.03 inch e.g., 0.005 inch, 0.007 inch, 0.008 inch. Layering andstacking the first electrode, insulating layer and second electrode asdepicted in FIG. 2 maintains a substantially flat profile against theouter surface of the elongate member, while maintaining a coaxialelectrode configuration for efficient shockwave production. That is,such a configuration may be electrically similar to a traditionalcoaxial lithotripsy assembly having an inner electrode and an outerelectrode surrounding the inner electrode, but without substantiallyincreasing the crossing profile of the elongate member. For example,electrode assembly 200 may have a small enough thickness such that itdoes not extend more than 0.015 inch from the outer diameter of theelongate member 20. By applying a high voltage pulse between firstelectrode 1 and second electrode 3 in a fluid filled balloon thatencloses the shockwave electrode assembly, an electrohydraulic shockwavecan be generated that propagates outward from the side of the elongatemember 20. The gap that the current must cross may be at least partiallydetermined by the size and location of the opening 7 in the insulatinglayer 2 and the size and location of the opening 8 in the secondelectrode 3. For example, the opening 7 in the insulating layer may belarger than the opening 8 in the second electrode. The opening 7 in theinsulating layer may have a diameter from about 0.004 inch to about0.010 inch, e.g., about 0.008 inch, and the opening 8 in the secondelectrode may have a diameter from about 0.010 inch to about 0.02 inch,e.g., about 0.012 inch, 0.016 inch, 0.018 inch. The ratio of thediameters between the openings 7, 8 may be varied to adjust the forceand duration of the generated shockwave. In some variations, the ratiobetween the diameter of the opening 7 in the insulating layer and thediameter of the opening 8 in the second electrode may be about 0.5,e.g., 0.56. In some variations, the gap between the openings 7, 8 may berelated to the thickness of the insulating layer. For example, the gapbetween the openings may be 0.5*(diameter of opening 8−diameter ofopening 7)+thickness of the insulating layer 2. The desired gap size mayvary according to the magnitude of the high voltage pulse applied to thefirst electrode 1. For example, a gap of about 0.004 inch to about 0.006inch may be effective for shockwave generation using voltage pulses ofabout 3,000 V.

Another variation of a layered or stacked shockwave electrode assemblymay comprise an inner electrode located along or recessed within theouter surface of an elongate member, an insulating layer or sheath thatcircumferentially wraps the elongate member, and an outer electrode thatcircumferentially wraps around the elongate member and over theinsulating sheath. For example, the first electrode may be pressed intothe outer surface of the elongate member, and attached to the elongatemember by an adhesive (e.g., a conductive adhesive such as conductiveepoxy), crimping, welding, and/or pinching. FIGS. 3A-3E depict onevariation of a low profile shockwave device 300 comprising an elongatemember 320, an inner electrode 306 pressed into and/or recessed withinthe outer wall of the elongate member 320, an insulating layer 302disposed over the first electrode 306 such that a first opening 307 a inthe insulating layer is located over the first electrode, and an outerelectrode 308 disposed over the insulating layer 302 such that a firstopening 317 a in the outer electrode is coaxially aligned with the firstopening 307 a in the insulating layer. The insulating layer 302 and theouter electrode 308 may each be in the form of a sheath or band, wherethe insulating sheath may be placed and/or wrapped over the innerelectrode and the second electrode sheath may be placed and/or wrappedover the insulating sheath such that the openings in the insulatingsheath and outer electrode sheath are coaxially aligned. In somevariations, the openings in the insulating sheath and outer electrodesheath are circular and are coaxially aligned such that the centers ofthe openings are aligned along the same axis and/or concentric. Theinsulating layer, outer electrode, and second inner electrode may bestacked such that the center of the first opening in the insulatinglayer, the center of the first opening in the outer electrode, and thefirst inner electrode are aligned on the same axis. The elongate membermay comprise a longitudinal lumen 304 along at least a portion of itslength, where the lumen 304 may be configured for passing variousinstruments and/or a guide wire therethrough. In some variations, theelongate member may be a catheter with a guide wire lumen. The elongatemember may also comprise one or more conductors that may extend alongthe length of the elongate member to connect the inner and/or outerelectrode to a high voltage pulse generator. For example, the elongatemember may comprise a first wire 305 and a second wire 310 that may beextruded within the walls of the elongate member 320, as depicted inFIG. 3B. Alternatively, the wires could be located in additionallongitudinal lumens of the elongate member and/or be located inlongitudinal grooves along the outer surface of the elongate member. Thewires 305 and 310 may be surrounded by the insulating material of theelongate member and are therefore electrically insulated from eachother. Alternatively or additionally, the wires may each have insulatingsleeves that wrap around them. The conductive portion of the wires maybe exposed at certain locations along its length to contact the innerand outer electrodes. The wires may contact the inner and outerelectrodes by soldering, crimping, stapling, pinching, welding,conductive adhesive (e.g., using conductive epoxy), and the like, asfurther described below. In some variations, the inner electrode may bea hypotube that is crimped to the wire. The connectivity between theconductors and the inner and outer electrodes may be such that the innerelectrode is the positive terminal and the outer electrode is thenegative terminal (or vice versa). Such a configuration may allow ashockwave generated between the inner and outer electrodes to propagateoutward from the side of the elongate member.

Optionally, a shockwave device may have more than one low-profileelectrode assembly along the side of the elongate member. In somevariations, a first electrode assembly may be located along a side ofthe elongate member while a second electrode assembly may be located onthe opposite side of the elongate member (i.e., 180 degrees from eachother). For example and as depicted in FIGS. 3A-3E, the shockwave device300 may comprise a second inner electrode 330 pressed into and/orrecessed within the outer wall of the elongate member 320, opposite thefirst electrode 306. The elongate member may further comprise a thirdwire 309 to connect the second inner electrode 330 to a high voltagepulse generator. The insulating layer 302 and the outer electrode mayeach have an additional opening 307 b, 317 b (respectively) that arecoaxially aligned with each other and with the second inner electrode330. The insulating layer, outer electrode, and second inner electrodemay be stacked such that the center of the second opening in theinsulating layer, the center of the second opening in the outerelectrode, and the second inner electrode are aligned on the same axis.The first electrode assembly 340 may comprise the first inner electrode306, the insulating layer 302 with the first opening 307 a aligned overthe first inner electrode, and the outer electrode 308 with the firstopening 317 a coaxially aligned with the first opening 307 a of theinsulating layer. The second electrode assembly 350 may comprise thesecond inner electrode 330, the insulating layer 302 with the secondopening 307 b aligned over the second inner electrode, and the outerelectrode 308 with the second opening 317 b coaxially aligned with thesecond opening 307 b of the insulating layer. By sharing the sameinsulating layer 320, the first coaxial electrode assembly and thesecond coaxial electrode assembly may be located at the samelongitudinal position along the elongate member. A shockwave devicecomprising two or more low-profile electrode assemblies located at thesame longitudinal position may allow for shockwaves to propagate outwardfrom the elongate member with various angular spread (e.g., up to 360degree angular spread). For example, a first shockwave generated by thefirst electrode assembly may propagate outward with an angular spread ofabout 180 degrees around the elongate member and a second shockwavegenerated by the second electrode assembly located opposite the firstelectrode assembly (e.g., 180 degrees from the first electrode assembly)may propagate outward with an angular spread of about 180 degrees aroundthe other side of elongate member, for a cumulative spread of 360degrees around the elongate member. In other variations, a shockwavedevice may comprise three or more electrode assemblies, where the threeor more electrode assemblies may also be located at the samelongitudinal location, but located at different circumferentiallocations. For example, there may be an additional third electrode andfourth inner electrode around the circumference of the elongate member.The insulating layer may have additional openings aligned over theadditional third and fourth inner electrodes, and the outer electrodemay have additional openings aligned over the openings of the insulatinglayer. The third and fourth electrode assemblies formed by the third andfourth inner electrodes and the additional openings in the insulatinglayer and outer electrode may allow for the generation of fourshockwaves from the same longitudinal location along the elongatemember. For example, the first, second, third and fourth electrodeassemblies may be at the same position along the length of the elongatemember, but be circumferentially distributed around the elongate member90 degrees apart from each other (i.e., the first electrode assembly maybe at position 0 degrees, the second electrode assembly may be aposition 180 degrees, the third electrode assembly may be at position 90degrees, and the fourth electrode assembly may be at 270 degrees). Thismay give rise to four shockwaves that propagate outward, each fanningout with an angular spread of about 90 degrees. The assembly of ashockwave device with two low-profile electrode assemblies at the sameposition along the length of the elongate member is described below, butit should be understood that similar methods may be used to assembleshockwave devices with three or more low-profile electrode assemblies atthe same longitudinal position along the length of the elongate member.

As depicted in FIG. 3B, the first inner and second inner electrodes 306,330 may be pronged electrodes 306 a, 330 a and may be shaped to bepressed into the wall of the insulating material of the elongate member.Electrical contact between the first inner and second inner electrodesand the first and third wires may be attained via finger extensions ofthe pronged electrodes. The pronged electrodes 306 a, 330 a may havefinger extensions 306 b, 330 b that pinch the first and third wires 305,309 (respectively) in the wedge of the fingers. The pronged electrodesmay also be electrically connected to the wires by any suitable method,for example, soldering, crimping, welding, conductive adhesives (e.g.,using conductive epoxies), pressure fit, interference fit, etc. FIG. 3Cdepicts the first inner and second inner electrode pressed into the sideof the elongate member such that the first inner electrode and secondinner electrode make electrical contact with the first and third wireswithin the elongate member. The pronged electrodes 306 a, 330 a may formthe first layer of a stacked low-profile shockwave electrode assembly(e.g., similar to the layered or stacked configuration of the electrodeassembly depicted in FIG. 2). The pronged electrodes may comprisetungsten, stainless steel, platinum iridium, nickel, iron, steel, and/orother electrically conductive material.

The insulating sheath 302 may circumferentially wrap around the elongatemember 320 such that it overlaps with and overlays the first innerelectrode and second inner electrode, as depicted in FIG. 3D. Theinsulating sheath 302 may overlap and stack on top of the first innerelectrode and second inner electrode 306 and 330 such that the firstopening 307 a is coaxially aligned with the first inner electrode andthe second opening 307 b is aligned with the second inner electrode. Theinsulating sheath 302 may be made of any material that has a highbreakdown voltage, such as Kapton, polyimide, ceramic, Teflon, or anycombination of such materials. The insulating sheath 302 may be placedover the elongate member by sliding it from one end of the elongatemember to the desired location. The insulating sheath 302 may be securedin the desired location by friction fit, adhesive, welding, crimping, orany other suitable method.

The outer electrode 308 may be a sheath or band that may be configuredto stack on top of and/or wrap over the insulating layer 302, as shownin FIG. 3E. The outer electrode 308 may have an extension 319 withpointed fingers 318 configured to penetrate the elongate member tocontact the second wire 310 (e.g., by crimping the fingers 318 so thatthe fingers are pressed into and on the wire 310). The outer electrode308 may be a metallic sheath or band that may wrap or enclose theelongate member. The outer electrode 308 may be positioned such that thefirst opening 317 a is coaxially aligned with the first opening 307 a ofthe insulating sheath 302 and the second opening 317 b is coaxiallyaligned with the second opening 307 b of the insulating sheath. In somevariations, the outer electrode 308 may be slid over one end of theelongate member and moved longitudinally into the desired position,after which it may be secured by friction fit, conductive adhesive(e.g., using conductive epoxy), welding, soldering, crimping, or anyother suitable method. The outer electrode 308 may be made of copper,stainless steel, platinum/iridium or other electrically conductivematerials.

As described above, the first inner electrode may be connected to thefirst wire 305 and the second inner electrode may be connected to thethird wire 309. In some variations, the high voltage pulse generator maydrive the first wire 305 and third wire 309 together or independently.For example, the pulse generator may apply voltage pulses simultaneouslyto both wires, and/or may apply voltage pulses sequentially (e.g., avoltage pulse is applied to the first wire without applying a pulse tothe third wire, or vice versa). The voltage pulses applied to the thirdwire may be delayed with respect to the voltage pulses applied to thefirst wire. In some variations, a multiplexor may be used with the highvoltage pulse generator to control application of pulses between thefirst and third wires. This may allow shockwaves with differentfrequency, magnitude, and timing to be generated on either side of theelongate member. For example, in some procedures it may be desirable toapply shockwaves on one side of the elongate member but not on the otherside (e.g., in an angioplasty procedure where there is a calcifiedlesion in one portion of the vessel but not in other portions of thevessel). The first, second, and third wires may be directly connected toa high voltage pulse generator, or may first connect to a connector thatis then plugged into the high voltage pulse generator.

One example of a shockwave device comprising one or more of thelow-profile electrode assemblies described above is depicted in FIG. 4.The shockwave device depicted there may be suitable for use in anangioplasty or valvuloplasty procedure. Shockwave device 400 maycomprise a catheter 402, a first low-profile coaxial electrode assembly404, a second low-profile coaxial electrode assembly 406 (not visible inthis view), and a balloon 408 enclosing the portion of the elongatemember where the first and second electrode assemblies are located. Theballoon may be made of an electrically insulating material that may berigid (e.g., PET, etc.), semi-rigid (e.g., PBAX, nylon, PEBA,polyethylene, etc.), or flexible (e.g., polyurethane, silicone, etc.).The first and second electrode assemblies may be located radially acrossfrom each other such that the shockwaves they each generate propagate inopposite directions. The shockwaves generated by each of the electrodeassemblies may propagate outward, with an angular spread of 180 degrees.The inner electrodes of each of the electrode assemblies may beconnected to conductors within the catheter 402, which may be connect toa high voltage pulse generator. In some variations, the high voltagepulse generator may be a 2 kV to 6 kV, e.g., 3 kV, pulsed power supply.The inner electrode of the first electrode assembly may be connected toa first positive lead of the pulse generator while the inner electrodeof the second electrode assembly may be connected to a second positivelead of the pulse generator. The outer electrode may be connected to anegative lead of the pulse generator, or to ground. The first and secondpositive leads of the pulse generator may be pulsed simultaneously orseparately, and may be controlled together or separately controlled(e.g. using a multiplexor), as described previously.

Additional low-profile shockwave electrode assemblies may alternativelyor additionally be located along a plurality of locations along thelength of the elongate member. For example, the low-profile coaxialshockwave electrode assemblies described above may be linearly arrangedalong the longitudinal length of the elongate member. Additionalvariations of shockwave devices with a plurality of electrode assembliesare described below.

One example of a shockwave device which may be configured for shockwaveangioplasty is depicted in FIG. 5A-5F. Shockwave angioplasty system 520may comprise a catheter 522, a proximal hub 524, one or more shockwaveelectrode assemblies 526 at a distal portion of the catheter, ahigh-voltage connector 530 for connecting the shockwave assemblies to apulse generator, and an angioplasty balloon 528 configured to beinflated with a fluid. A proximal portion of the wires from theshockwave assemblies may form a cable 576 that may be enclosed in ajacket. The cable may extend from a lumen of the proximal hub 524 andconnect to the high-voltage connector 530. Pins within the high-voltageconnector may connect each of the wires from the shockwave assemblies tothe appropriate channel on a high voltage pulse generator. Optionally,the system 520 may additional comprise a strain relief tube 532connected to the hub 524. The catheter 522 may have a guide wire lumentherethrough. There may be any number of shockwave electrode assemblieslocated at the distal end of the catheter and enclosed by the balloon.For example, there may be one shockwave electrode, two shockwaveelectrode assemblies, four shockwave electrode assemblies, fiveshockwave electrode assemblies or more. FIGS. 5B and 5C depict thedistal portions of shockwave devices with two electrode assemblies andfive electrode assemblies. FIG. 5B depicts one variation of a shockwavedevice 500 comprising an elongate member 502, a first electrode assembly504 at a first location along the length of the elongate member, asecond electrode assembly 506 at a second location along the length ofthe elongate member, and a balloon 508 configured to be filled with afluid to sealably enclose the first and second electrode assemblies. Theballoon 508 may be made of an electrically insulating material that maybe rigid (e.g., PET, etc.), semi-rigid (e.g., PBAX, nylon, PEBA,polyethylene, etc.), or flexible (e.g., polyurethane, silicone, etc.).The first and second electrode assemblies may be spaced apart along thelength of the elongate member, and may be from about 3 mm to about 20 mmapart from each other, e.g., about 5 mm, 7 mm, 10 mm. The length of theballoon may vary depending on the number of electrode assemblies and thespacing between each of the electrode assemblies. For example, a balloonfor a shockwave device with two electrode assemblies spaced about 7 mmapart (e.g., 6.7 mm) may have a length of about 20 mm. A balloon for ashockwave device with five electrode assemblies spaced about 10 mm apartmay have a length of about 60 mm. The electrode assemblies 504, 506 eachcomprise two inner electrodes that are positioned circumferentiallyopposite each other, an insulating sheath with two openings aligned overthe two inner electrodes, and an outer electrode sheath with twoopenings that are coaxially aligned with the two openings of theinsulating sheath. Each of the electrode assemblies 504, 506 areconfigured to generate a pair of directed shockwaves, where theshockwaves resulting from a high voltage pulse to the first innerelectrode propagate in a direction that is opposite to the direction ofthe shockwaves resulting from a high voltage pulse to the second innerelectrode. The electrode assemblies 504, 506 may generate shockwavesthat propagate outward from different locations around the circumferenceof elongate member 502. For example, the electrode assembly 504 maygenerate shockwaves that propagate from the left and right longitudinalside of the elongate member, while the electrode assembly 506 maygenerate shockwaves that propagate from the top and bottom longitudinalside of the elongate member. In some variations, the electrode assembly504 may generate a pair of shockwaves that propagate outward frompositions at 0 degrees and 180 degrees around the circumference of theelongate member 502, while the electrode assembly 506 may generate apair of shockwaves that propagate outward from positions at 60 degreesand 240 degrees around the circumference of the elongate member. Instill other variations, electrode assemblies 504, 506 may each generatea pair of shockwaves that propagate outward at the same locations aroundthe circumference of the elongate member, but from different locationsalong the length of the elongate member. Optionally, a radiopaque markerbands may be provided along the length of the elongate member to allow apractitioner to identify the location and/or orientation of theshockwave device as it is inserted through the vasculature of a patient.For example, there may be a first marker band proximal to the firstelectrode assembly and a second marker band distal to the secondelectrode assembly. In some variations, one or more marker bands may belocated proximal to the proximal-most electrode assembly, and/or distalto the distal-most electrode assembly, and/or in the center of theelongate member and/or any other location along the length of theelongate member.

FIG. 5C depicts another shockwave device 550 comprising an elongatemember 552, a first electrode assembly 554, a second electrode assembly556, a third electrode assembly 558, a fourth electrode assembly 560, afifth electrode assembly 562, and a balloon 564 configured to be filledwith a fluid to sealably enclose the first, second, third, fourth, andfifth electrode assemblies. The balloon 564 may be made of anelectrically insulating material that may be rigid (e.g., PET, etc.),semi-rigid (e.g., PBAX, nylon, PEBA, polyethylene, etc.), or flexible(e.g., polyurethane, silicone, etc.). The electrode assemblies ofshockwave device 550 may be similar to the ones described in FIG. 5B,and/or may be similar to any of the electrodes described herein. Theelongate member may be a catheter with a longitudinal guide wire lumen.Each of the electrode assemblies are configured to generate a pair ofshockwaves that propagate in two opposite directions from the side ofthe elongate member. The electrode assemblies of FIG. 5C may beconfigured to generate shockwaves that propagate outward from differentlocations around the circumference of elongate member, as describedabove for FIG. 5B. Although the figures herein may depict shockwavedevices with two or five electrode assemblies, it should be understoodthat a shockwave device may have any number of electrode assemblies, forexample, 3, 4, 6, 7, 8, 9, 10, 15, 20, etc. The electrode assemblies maybe spaced apart along the length of the elongate member, and may be fromabout 3 mm to about 10 mm apart from each other, e.g., about 5 mm, 8 mm,10 mm, etc. depending on the number of electrode assemblies and thelength of the elongate member that is enclosed within the balloon.Shockwave devices with a plurality of electrode assemblies distributedalong the length of a catheter may be suitable for use in angioplastyprocedures to break up calcified plaques that may be located along alength of a vessel. Shockwave devices with a plurality of electrodeassemblies along the length of a curved elongate member may be suitablefor use in valvuloplasty procedures to break up calcified plaques thatmay be located around the circumference of a valve (e.g., at or aroundthe leaflets of a valve). The electrode assemblies of FIGS. 5A-5C may besimilar to the electrode assemblies described above and depicted inFIGS. 3A-3E, and/or may be any of the electrode assemblies describedbelow.

FIGS. 5D and 5E are detailed views of the proximal hub 524. As shownthere, proximal hub 524 may comprise a central shaft 542, a first sideshaft 540 and a second side shaft 544. The first and second side shaftsare attached to either side of the central shaft 542. The central shaft542 may have a proximal opening 548 that is connected to an inner lumen543 that extends through the length of the central shaft and terminatesat a distal opening 546 that is configured to interface with the strainrelief and the catheter 522. The inner lumen 543 may be in communicationand/or continuous with the guide wire lumen of the catheter 522. Thefirst side shaft 540 may have an opening 547 that is connected to aninner lumen 541, which is in communication and/or continuous with theinner lumen 543 of the central shaft 542. The second side shaft 544 mayhave an opening 549 that is connected to an inner lumen 545. The innerlumen 545 of the second side shaft 544 may not be connected to thecentral inner lumen 543. The inner lumens 541, 543, 545 may each have awider proximal region and a narrower distal region, which may act as astop for the devices inserted into the shafts. The central shaft 548 andits inner lumen 543 may function as a port for the insertion of aguidewire and/or to deliver an imaging contrast agent to the distal endof the catheter 522. The first side shaft 540 and inner lumen 541 mayfunction as an inflation port for saline and/or imaging contrast agent.The second side shaft 549 and inner lumen 545 may function as a portthrough which the cable 576 may extend and connect to the high voltageconnector 530 to electrically connect a high voltage pulse generator tothe shockwave electrode assemblies at the distal end of the catheter.The cable 576 may be bonded to the connector 530 and/or the hub. In somevariations, the proximal hub 524 may be made of injection moldedpolycarbonate. The length L1 of the central shaft 542 may be from about2 inches to about 4 inches, e.g., about 2.3 inches or 2.317 inches,while the length L2 of the side shafts 540, 544 may be from about 1 inchto about 2 inches, e.g., about 1.4 inches or 1.378 inches. The diameterD1 of the narrowest portion of the central inner lumen D1 may be fromabout 0.05 inch to about 0.1 inch, e.g., about 0.08 inch to about 0.082inch.

FIG. 5F is a detailed view of the high voltage connector 530 that may beinserted through at least one of the ports of the proximal hub, andconfigured to connect the shockwave electrode assemblies 526 to a highvoltage pulse generator. The high voltage connector 530 may have aproximal port 570 that is configured to connect with a port of a highvoltage pulse generator, a first shaft region 572, and a second shaftregion 574 that is narrower than the first shaft region 572 that mayconnect to cable 576. The first shaft region 572 may have a diameter D3that is greater than the diameter of the narrower portion of an innerlumen of the proximal hub, but smaller than the diameter of the widerportion of the inner lumen. The second shaft region 574 distal to thefirst shaft region may be configured for strain relief. For example, thecable 576 may provide connections for both the high voltage pulse(s) andthe return path between the voltage pulse generator and the electrodeassemblies. In some variations, the cable may provide one or more highvoltage supply connections to the electrode assemblies, with one or morereturn connections. For example, the cable may provide for a single highvoltage supply connection and a single return connection to theelectrode assemblies. Alternatively, the cable may provide for aplurality of high voltage supply connections (e.g., four) and one ormore return connections to the electrode assemblies. The proximal port570 may have a length L3 from about 1.5 inches to about 3 inches, e.g.,about 2 inches or 2.059 inches, and a diameter D2 from about 0.2 inch toabout 1 inch, e.g., about 0.7 inch or 0.72 inch. The diameter D3 of thefirst shaft region 572 may be from about 0.05 in to about 0.2 inch,e.g., about 0.1 inch or 0.112 inch.

FIG. 6A depicts another variation of a low-profile coaxial shockwaveelectrode assembly that may be used in any of the shockwave devicesdescribed herein. The electrode assembly 600 may comprise a first innerelectrode 604, an insulating layer or sheath 606 disposed over the firstinner electrode and circumferentially wrapped around an elongate member602 (e.g., a catheter with a guidewire lumen), and an outer electrodesheath 608 disposed over the insulating sheath. While the insulatingsheath is depicted as fully circumscribing the elongate member, itshould be understood that in other variations, an insulating layer maynot fully circumscribe the elongate member, and may instead be disposedover certain portions of the elongate member. The insulating sheath 606may have a first opening 607 a that is coaxially aligned over the firstinner electrode 604, and the outer electrode sheath 608 may have a firstopening 609 a that is coaxially aligned over the first opening of theinsulating sheath. The electrode assembly 600 may also comprise a secondinner electrode that is circumferentially opposite (or otherwisedisplaced from) the first inner electrode (and therefore not depicted inthe view shown in FIG. 6A). The insulating sheath may have a secondopening 607 b that is coaxially aligned over the second inner electrode,and the outer electrode sheath may have a second opening 609 b that iscoaxially aligned over the second opening of the insulating sheath. Thefirst inner electrode coaxial with the first openings in the insulatingsheath and the outer electrode sheath may generate a first shockwavethat propagates outwards in a first direction and the second innerelectrode coaxial with the second openings in the insulating sheath andthe outer electrode sheath may generate a second shockwave thatpropagates outwards in a second direction that is opposite to the firstdirection. The diameter of the openings in the outer electrode sheathmay be larger than the diameter of the openings in the insulatingsheath. The size of and ratio between the diameter of the openings inthe outer electrode and the openings in the insulating sheath may beadjusted to attain the desired shockwave characteristics, as describedabove. The edges of the openings in any of the outer electrodesdescribed herein may be electropolished. Alternatively, some variationsof an electrode assembly may not have an insulating sheath or layerdisposed over the elongate member, but may instead comprise an innerelectrode having an insulating coating directly applied over the innerelectrode (e.g., disposed over the crimped hypotube of the innerelectrode). The insulating coating may cover the inner electrode suchthat a region of the conductive portion of the inner electrode isexposed, while the rest of the inner electrode is covered by thecoating. The opening in the outer electrode sheath may be coaxiallyaligned with the exposed region of the inner electrode. The thicknessand/or material of the insulating coating may be varied depending on themagnitude of the voltage to be applied on the electrode. Examples ofinsulating coatings may be Teflon, polyimide, etc. Using an insulatingcoating on the inner electrode instead of an insulating layer disposedover the elongate body may further reduce the crossing profile of theelectrode assembly, and may allow for more bending or a tighter turningradius than an electrode assembly having an insulating sheath.

The inner electrodes and the outer electrode may each be connected to ahigh voltage pulse generator via a plurality of wires 610 that may belocated within a plurality of longitudinal grooves 601 along the outersurface of the elongate member 602 (e.g., a catheter having a guidewirelumen) of the shockwave device. The wires may be electrically insulatedalong its length (e.g., by an insulating coating or sheath made of, forexample, polyimide, PEBA, PET, FEP, PTFE, etc.) except for one or moreregions where the electrically conductive core of the wire is exposed tocontact a portion of the inner and/or outer electrode. For example, theinsulating coating or sheath at the distal tip of the wire may bestripped to expose the conductive portion. The wires may be made of anyconductive material, for example, free oxygen copper or copper orsilver. The inner electrode 604 may be a hypotube that is crimped overthe distal tip of the wire 610, where the wire 610 is enclosed withinone of a plurality of grooves 601 of the elongate member. The hypotubemay be made of stainless steel, tungsten, a platinum-iridium alloy, orany other material with similar hardness. In variations of an electrodeassembly without an insulating layer disposed over the elongate member,a portion of the hypotube may be coated with an insulating material asdescribed above. Each groove of the elongate member may partiallyenclose a single wire. For example, the wire 610 may be half enclosedwithin a groove of the elongate member, such that half of the wire isrecessed or embedded within the groove and half of the wire protrudesoutside of the groove. The wire 610 may be slidably disposed within thegroove. As the elongate member is curved or bent (e.g., during anangioplasty procedure where the elongate member is a catheter that isadvanced through a patient's vasculature), the wire may slide within thegroove to accommodate changes in the radius of curvature as the elongatemember bends, thereby minimally interfering with the flexibility of theelongate member. Optionally, one or more shrink tubes may be provided toretain the wire within the groove without impinging on its ability tomove and shift as the elongate member bends or curves. For example, oneor more bands of shrink tubes may be located circumferentially aroundthe distal portion of the elongate member. Alternatively or additionallyor optionally, dots of epoxy may be applied along a distal length of thewires to partially secure or retain the wires within the grooves whilestill maintaining the ability of the wires to partially move and shiftas the elongate member bends or curves. In some variations, the wiresmay slide within the grooves without any retaining elements. Additionaldetails regarding the longitudinal grooves of the elongate member areprovided below.

FIGS. 6B and 6C depict perspective and side view of the outer electrodesheath 608. In some variations, the outer electrode may be a radiopaquemarker band (e.g., marker band used in angioplasty procedures). Asdepicted there, the first opening 609 a may be located directly acrossfrom the second opening 609 b. FIG. 6D depicts a perspective view of theinsulating sheath 606 having a first opening 607 a and a second opening607 b located directed across from the first opening 607 a. As describedabove, each of these openings may be coaxially aligned with the openingsof the insulating sheath 606 and first and second inner electrodes toform two shockwave sources capable of generating two shockwaves thatpropagate outward from the side of the elongate member in two oppositedirections. FIGS. 6E and 6F depict another variation of an outerelectrode sheath 620 that comprises two openings 622 a, 622 b that arecircumferentially across each other, but laterally offset. The diameterof each of the openings 622 a, 622 b may be from about 0.010 inch toabout 0.024 inch, e.g., about 0.014 inch. FIG. 6G depicts a variation ofan insulating sheath 630 that comprises two openings 632 a, 632 b thatare circumferentially across each other, but laterally offset. Thediameter of each of the openings 632 a, 632 b may be from about 0.004inch to about 0.01 inch, e.g., about 0.008 inch. The size and ratio ofthe openings in the insulating sheath and the outer electrode may besimilar to those described previously (see FIG. 2 and accompanyingdescription). The openings 622 a, 622 b of the outer electrode sheathmay be coaxially aligned with the openings 632 a, 632 b of theinsulating sheath 630, respectively. The outer electrode sheath 620 andthe insulating sheath 630 may be used with a pair of inner electrodesthat are similarly circumferentially across each other, but laterallyoffset such that the two inner electrodes are each coaxially alignedwith the each of the openings in the insulating sheath and the outerelectrode sheath. This may functionally create two shockwave sourcesconfigured to generate two shockwaves that propagate outward in twodirections that are opposite each other but laterally offset.

In the variations of the shockwave electrode assemblies described above,the inner electrode is retained within a longitudinal groove of acatheter, and the openings of an insulating sheath and outer electrodeare coaxially aligned with the inner electrode. As a result, thecircumferential position of the openings in the insulating sheath andthe outer electrode (and therefore, the circumferential position of ashockwave source) may be constrained by the circumferential position ofthe longitudinal groove that retains the inner electrode. In somevariations, it may be desirable to position a shockwave source at acircumferential position around the elongate member that is differentfrom the circumferential position of the groove that retains the innerelectrode. That is, the location of the shockwave source as defined bythe circumferential location of the openings in the insulating sheathand outer electrode sheath may be offset with respect to the groove. Across-section of such shockwave electrode assembly is depicted in FIG.6H. Depicted there is a catheter 640 with a central guide wire lumen 641and first and second grooves 642 a, 642 b that are locatedcircumferentially opposite each other (e.g., 180 degrees around thecatheter). First and second wires 644 a, 644 b are retained within thegrooves 642 a, 642 b and are connected to first and second innerelectrodes 646 a, 646 b. The first and section wire 644 a, 644 b andgrooves 642 a, 642 b are aligned along axis 654. However, it may bedesirable to have a shockwave source be located at a location that isoffset from a first axis 654, for example at a location that is radiallyoffset by angle A1 (which may be from about 1 degree to about 179degrees). To form a shockwave electrode assembly that is offset by angleA1 from the first axis 654, the first and second inner electrodes 646 a,646 b may each be a hypotube that is asymmetrically crimped so that alength of the hypotube circumferentially spans a portion of thecatheter. For example, in the variation shown in FIG. 6H, the innerelectrodes 646 a, 646 b may span at least an angle A1 along thecircumference of the catheter 640. The first and second openings 647 a,647 b of the insulating sheath 648 may be coaxially aligned over thefirst and second inner electrodes at the radially offset location, andthe first and second openings 651 a, 651 b of the outer electrode 650may be coaxially aligned over first and second openings 647 a, 647 b ofthe insulating sheath 648. In other words, the first and second openings647 a, 647 b of the insulating sheath 648, the first and second openings651 a, 651 b of the outer electrode 650, and a portion of the first andsecond inner electrodes 646 a, 646 b may be coaxially aligned along asecond axis 652 that is offset by angle A1 from the first axis 654. Suchconfiguration may allow for the placement of a shockwave source anywherealong the circumference of a catheter without necessarily being alignedwith the circumferential location of the one more longitudinal groovesof the catheter.

The low-profile shockwave electrode assembly depicted in FIG. 6A may beassembled in any suitable fashion. FIGS. 7A-7D depict an example of amethod for making a low-profile shockwave electrode assembly that islocated along a length of an elongate member (which for claritypurposes, is not shown here). The inner electrode 700 may be a hypotubethat is placed over an exposed core of a wire 702 and crimped andflattened, as illustrated in FIGS. 7A and 7B. In some variations, theinner electrode 700 may be crimped and flattened with a slight curve toapproximate and/or match the radius of curvature of the elongate member.The inner electrode 700 and the wire 702 are then placed within alongitudinal groove of the elongate member (see FIG. 6A). An insulatinglayer or sheath 704 may be slid over the elongate member and positionedover the inner electrode 700 such that an opening 705 of the insulatingsheath 704 is coaxially aligned over the inner electrode, as shown inFIG. 7C. An outer electrode sheath 706 may be slid over the elongatemember and positioned over the insulating sheath 704 such that anopening 707 of the outer electrode sheath 706 is coaxially aligned overthe opening 705 of the insulating sheath 704, as shown in FIG. 7D. Invariations of shockwave electrode assemblies that comprise a secondinner electrode circumferentially opposite to the first inner electrode700, aligning the openings of the insulating sheath and the outerelectrode over the first inner electrode may also align a second set ofopenings of the insulating sheath and the outer electrode over thesecond inner electrode. Once the outer electrode sheath and theinsulating sheath have been positioned in the desired location, theirlocation may be secured by applying a UV curable adhesive, such asLoctite 349, at both ends of the sheaths.

FIGS. 8A and 8B depict side and cross-sectional view (taken along line8B-8B) of one variation of a grooved elongate member (e.g., a catheter)that may be used in any of the shockwave devices described herein. Theelongate member 802 may have any number of longitudinal grooves orchannels configured for retaining a wire and/or inner electrode, and mayfor instance have 1, 2, 3, 4, 5, 6, 7, 8, 10, etc. grooves. Asillustrated in FIG. 6B, the elongate member 602 has six grooves thatsurround a central guide wire lumen 603. In some variations, theelongate member 802 may have a radius of about 0.014 inch and the eachof the grooves may have a radius of curvature of about 0.005 inch toabout 0.010 inch. Where the grooves may have a semi-elliptical shape,the minor axis may be about 0.008 inch and the minor axis may be about0.015 inch. The elongate member 802 may also comprise a guide wire lumen803, where the guide wire lumen may have a radius of about 0.0075 inchto about 0.018 inch, e.g., about 0.02 inch or 0.0175 inch.

Optionally, shrink tubing may be provided over each of the wires to helpretain the wire within the groove while still allowing the wires toslide and move within the grooves to accommodate bending of the elongatemember 602. Wires slidably disposed within longitudinal grooves on theouter surface of the elongate member may retain the flexibility of theelongate member such that the elongate member may easily navigate andaccess tortuous vasculature. While the variations here depict wires thatare slidably disposed within grooves of the elongate member toaccommodate bending of the elongate member, in other variations, thewires may be conductive elements that are co-extruded with the elongatemember and therefore unable to slide with respect to the elongatemember. However, co-extruding conductive elements with the elongatemember may stiffen the elongate member, thereby limiting its flexibilityand ability to navigate to and access tortuous vasculature. For example,the smallest radius of curvature attainable by an elongate member withco-extruded conductive elements may be larger than the smallest radiusof curvature attainable by an elongate member with wires slidablydisposed in grooves along its outer surface. The turning radius of anelongate member that has wires slidably disposed within longitudinalgrooves along its outer surface may be tighter than the turning radiusof the same elongate member if the wires were unable to slide withrespect to the elongate member.

The wires retained within the longitudinal grooves of an elongate membermay be connected to inner electrodes, as described above, and/or may beconnected to outer electrode sheaths. A wire that is retained within alongitudinal groove may be connected to an outer electrode sheath usingany suitable method, for example, by friction fit and/or adhesives. Forexample, the wire may be friction fit between the outer electrode sheathand the insulating sheath, and optionally further secured in contactwith the outer electrode sheath with an adhesive, as depicted in FIG. 9.As depicted there, a wire 900 retained within a groove 904 of anelongate member 902 may contact an outer electrode sheath 906 via astripped portion 910 that is drawn out of the groove 904 and insertedbetween the outer electrode sheath and insulating sheath 908 (forclarity, the inner electrode of this shockwave electrode assembly is notshown). The wire may be secured between the outer electrode sheath andthe insulating sheath friction fit and may optionally be further securedand electrically insulated by an adhesive, such as conductive epoxy orlaser welded or spot welded. Inserting the stripped portion 910 (wherethe electrically conductive portion is exposed) between the outerelectrode sheath and the insulating sheath and further sealing it withan adhesive may help to ensure that the wire does not inadvertentlycontact an inner electrode or any other conductive medium (e.g., thefluid that may be used to fill a shockwave angioplasty balloon). Variousconnections between the wires and the inner and outer electrodes of theelectrode assemblies are further described below.

The first and second inner electrodes of an electrode assembly may beconnected such that they are each independently voltage-controlled,e.g., each directly connect to separate positive channels of a highvoltage pulse generator. They may be independently controlled (e.g.,capable of being pulsed separately) or may be controlled together. Anexample of direct connectivity between the first and second innerelectrodes of a shockwave electrode assembly 1000 is depicted in FIGS.10A-10D. The shockwave electrode assembly 1000 may be any of theelectrode assemblies described herein, and may comprise a first innerelectrode 1002, a second inner electrode 1004 and an outer electrode1006. As schematically depicted in FIG. 7A, a first wire 1003 mayconnect the first inner electrode 1002 to a first voltage output portVO1 of a pulse generator 1001. A second wire 1005 may connect the secondinner electrode 1004 to a second voltage output port VO2 of the pulsegenerator 1001. A third wire 1006 may connect the outer electrode to athird voltage output port VO3 (a ground channel or negative terminal).In some variations, the first voltage output port VO1 and the secondvoltage output port VO2 may be positive channels while the third voltageoutput port VO3 may be a negative channel (or vice versa). During a highvoltage pulse on the first and/or second voltage output ports VO1, VO2,current may flow in the direction of the arrows in the first and/orsecond wires 1003, 1005 from the voltage outputs VO1, VO2 to the firstand second inner electrodes 1002, 1004. The high voltage pulse generatormay apply a voltage pulse on output port VO1 such that the potentialdifference between the first inner electrode 1002 and the outerelectrode 1006 is high enough to form a plasma arc between them,generating a bubble that gives rise to a shockwave. Similarly, the highvoltage pulse generator may simultaneously or sequentially apply avoltage pulse on output port VO2 such that the potential differencebetween the second inner electrode 1004 and the outer electrode 1006 ishigh enough to form a plasma arc between them, generating a bubble thatgives rise to a different shockwave. In a variation where the firstinner electrode and second inner electrode are located circumferentiallyopposite to each other (e.g., 180 degrees apart from each other aroundthe circumference of the elongate member), the shockwaves generated bythe first and second inner electrodes may propagate in oppositedirections, extending outward from the side of the elongate member. Thecurrent that traverses the bubble from the inner electrode 1002 and/orinner electrode 1004 to the outer electrode 1006 returns via wire 1007to voltage output port VO3 (which may be a negative channel or a groundchannel). Voltage output ports VO1 and VO2 may be independentlyaddressed (e.g., voltage and current may be applied to one output butnot necessarily the other), or may be not be independently addressed(e.g., activating one output necessarily activates the other).Optionally, a connector (not shown) may be provided between the wires1003, 1005, 1007 and the voltage pulse generator 1001 so that the wiresof the elongate member may be easily connected to the output ports ofthe high voltage generator.

FIGS. 10B-10D depict one variation of how the circuit of FIG. 10A may beimplemented in a shockwave device that comprises the shockwave electrodeassembly 1000. The shockwave device may comprise a catheter 1010 with acentral guide wire lumen 1011 and six longitudinal grooves (G1-G6)arranged around the guide wire lumen. FIG. 10B is a top view of theelectrode assembly 1000 where the first inner electrode 1002 is visibleand FIG. 10C a bottom view of the electrode assembly 1000 where thesecond inner electrode 1004 is visible. The first and second innerelectrodes are located circumferentially opposite each other (i.e., 180degrees apart). FIG. 10D depicts the grooves in which each of the innerelectrodes and/or wires may be retained. The return wire 1007 may beconnected to the outer electrode sheath 1006 in any of theconfigurations described above and may be retained in groove G3. Thewire 1003 connects the first inner electrode 1002 with the first voltageoutput VO1, and may be retained in groove G1. The wire 1005 connects thesecond inner electrode 1004 with the second voltage output VO2, and maybe retained in groove G4, directly opposite groove G1. While the exampledepicted here uses grooves G1, G3, and G4, it should be understood thatany three of the six grooves may be used to retain the wires 1003, 1005and 1007 to attain the connectivity depicted in FIG. 10A. For example,the wires 1003, 1005 and 1007 may be retained in grooves G2, G5 and G6respectively, or grooves G3, G6 and G5 respectively, or grooves G1, G3,and G2 respectively, grooves G1, G3, and G5 respectively, etc.

Alternatively, the first and second inner electrodes of an electrodeassembly may be connected in series such that activating the first innerelectrode also activates the second inner electrode. This may allow theelectrode assembly to generate up to two shockwaves (i.e., one from eachof the first and second inner electrodes) using only a single outputport on the high voltage generator. FIGS. 11A-11D depict one example ofa shockwave electrode assembly 1100 that is configured such that firstinner electrode 1102 is in series with the second inner electrode 1104.The shockwave electrode assembly 1100 may be any of the electrodeassemblies described herein, and may comprise a first inner electrode1102, a second inner electrode 1104 and an outer electrode 1106. Asschematically depicted in FIG. 11A, a first wire 1103 may connect thefirst inner electrode 1102 to a first voltage output port VO1 of a pulsegenerator 1101. A second wire 1105 may connect the second innerelectrode 1104 to a second voltage output port VO2 (a ground channel ornegative terminal). In some variations, the first voltage output portVO1 may be a positive channel while the second voltage output port VO2may be a negative channel (or vice versa). During a high voltage pulseon the first voltage output port VO1, current may flow in the directionof the arrow in the first wire 1103 from the voltage output VO1 to thefirst inner electrode 1102. The high voltage pulse generator may apply avoltage pulse on output port VO1 such that the potential differencebetween the first inner electrode 1102 and the outer electrode 1106 ishigh enough to form a plasma arc between them, generating a bubble thatgives rise to a shockwave. The current that traverses the bubble fromthe first inner electrode 1102 to the outer electrode 1106 may set up apotential difference between the outer electrode 1106 and the secondinner electrode 1004 that is high enough to form a plasma arc betweenthem, generating a bubble that gives rise to a different shockwave. In avariation where the first inner electrode and second inner electrode arelocated circumferentially opposite to each other (e.g., 180 degreesapart from each other around the circumference of the elongate member),the shockwaves generated by the first and second inner electrodes maypropagate in opposite directions, extending outward from the side of theelongate member. The current then returns to the voltage sourcegenerator via wire 1105 to voltage output port VO2 (which may be anegative channel or a ground channel). Optionally, a connector (notshown) may be provided between the wires 1103, 1105 and the voltagepulse generator 1101 so that the wires of the elongate member may beeasily connected to the output ports of the high voltage generator.

FIGS. 11B-11D depict one variation of how the circuit of FIG. 11A may beimplemented in a shockwave device that comprises the shockwave electrodeassembly 1100. The shockwave device may comprise a catheter 1110 with acentral guide wire lumen 1111 and six longitudinal grooves (G1-G6)arranged around the guide wire lumen. FIG. 11B is a top view of theelectrode assembly 1100 where the first inner electrode 1102 is visibleand FIG. 11C a bottom view of the electrode assembly 1100 where thesecond inner electrode 1104 is visible. The first and second innerelectrodes are located circumferentially opposite each other (i.e., 180degrees apart). FIG. 11D depicts the grooves in which each of the innerelectrodes and/or wires may be retained. The wire 1103 connects thefirst inner electrode 1102 with the first voltage output VO1, and may beretained in groove G1. The wire 1105 connects the second inner electrode1104 with the second voltage output VO2, and may be retained in grooveG4, directly opposite groove G1. While the example depicted here usesgrooves G1 and G4, it should be understood that any two of the sixgrooves may be used to retain the wires 1103, 1105 to attain theconnectivity depicted in FIG. 11A. For example, the wires 1103 and 1105may be retained in grooves G2 and G5 respectively, or grooves G3 and G6respectively, etc.

Some variations of shockwave devices may comprise two or more shockwaveelectrode assemblies. For example, the shockwave angioplasty system 520depicted in FIG. 5A comprises two electrode assemblies where eachelectrode assembly has two inner electrodes circumferentially oppositeto each other and is configured to generate two shockwaves thatpropagate outward from the side of the catheter in opposite directions.The two shockwave electrode assemblies may be connected such that eachof the inner electrodes of the two electrode assemblies (i.e., for atotal of four inner electrodes) are each connected to separate voltagechannels. For example, each of the inner electrodes may each be directlyconnected to different voltage channels in a direct connectconfiguration. The inner electrodes may be individually addressableand/or can be activated by separate ports on a high voltage pulsegenerator. FIGS. 12A-12D depict a variations of two shockwave electrodeassemblies of a shockwave device (e.g., a shockwave angioplasty device)where the first and second inner electrodes of each electrode assemblyare connected such that they are each connected to separate voltagechannels. The shockwave electrode assemblies 1200, 1250 may be any ofthe electrode assemblies described herein. The first shockwave electrodeassembly 1200 may comprise a first inner electrode 1202, a second innerelectrode 1204 and an outer electrode 1206. The second shockwaveelectrode assembly 1250 may comprise a first inner electrode 1252, asecond inner electrode 1254 and an outer electrode 1256. Asschematically depicted in FIG. 12A, a first wire 1203 may connect thefirst inner electrode 1202 of the first electrode assembly 1200 to afirst voltage output port VO1 of a pulse generator 1201. A second wire1205 may connect the second inner electrode 1204 of the first electrodeassembly 1200 to a second voltage output port VO2 of the pulse generator1201. A third wire 1207 may connect the outer electrode 1206 of thefirst electrode assembly to a third voltage output port VO3 (a groundchannel or negative terminal). In some variations, the first voltageoutput port VO1 and the second voltage output port VO2 may be positivechannels while the third voltage output port VO3 may be a negativechannel (or vice versa). A fourth wire 1253 may connect the first innerelectrode 1252 of the second electrode assembly 1250 to a fourth voltageoutput port VO4 of the pulse generator 1201. A fifth wire 1255 mayconnect the second inner electrode 1254 of the second electrode assembly1250 to a fifth voltage output port VO5 of the pulse generator 1201. Theouter electrode 1256 of the second electrode assembly may also contactthe third wire 1207 and be connected to the third voltage output portVO3. In some variations, the first voltage output port VO1, the secondvoltage output port VO2, the fourth voltage output VO4 and the fifthvoltage output VO5 may each be positive channels while the third voltageoutput port VO3 may be a negative channel. During a high voltage pulseon any one of the first and/or second and/or fourth and/or fifth voltageoutput ports VO1, VO2, VO4, VO5, current may flow in the direction ofthe arrows in the first and/or second and/or fourth and/or fifth wires1203, 1205, 1253, 1255 from the voltage outputs VO1, VO2, VO4, VO5 tothe first and second inner electrodes of the first and second electrodeassemblies 1202, 1204, 1252, 1254 of the first and second electrodeassemblies. The high voltage pulse generator may apply a voltage pulseon any one of the output ports such that the potential differencebetween any one of the inner electrodes and the corresponding outerelectrode 1206, 1256 is high enough to form a plasma arc between them,generating a bubble that gives rise to a shockwave. Each of the plasmaarcs formed between an inner electrode and an outer electrode (of thesame electrode assembly) may generate a bubble that gives rise to adifferent shockwave. In a variation where the first inner electrode andsecond inner electrode are located circumferentially opposite to eachother (e.g., 180 degrees apart from each other around the circumferenceof the elongate member), the shockwaves generated by the first andsecond inner electrodes may propagate in opposite directions, extendingoutward from the side of the elongate member. With the two electrodeassemblies 1200, 1250, a total of up to four different shockwaves may begenerated. The current that traverses the bubble from the innerelectrodes to the corresponding outer electrode returns via wire 1207 tovoltage output port VO3 (which may be a negative channel or a groundchannel). In some variations, the return current from any one of theouter electrodes may be connected to an intermediate node (e.g., anoptional outer electrode band or sheath, and/or optional interconnectwire) before it is connected to the wire 1207. The voltage output portsmay be independently addressed or may be not be independently addressed,as previously described. Optionally, a connector (not shown) may beprovided between the wires and the voltage pulse generator 1201 so thatthe wires of the elongate member may be easily connected to the outputports of the high voltage generator.

FIGS. 12B-12C depict one variation of how the circuit of FIG. 12A may beimplemented in a shockwave device that comprises the first shockwaveassembly 1200 and second shockwave electrode assembly 1250. Theshockwave device may comprise a catheter 1210 with a central guide wirelumen 1211 and six longitudinal grooves (G1-G6) arranged around theguide wire lumen. FIG. 12B is a perspective view of the distal portionof the shockwave device with the first electrode assembly 1200 andsecond electrode assembly 1250 each at different longitudinal locationsalong the catheter 1210. For each electrode assembly 1200, 1250, thefirst and second inner electrodes are located circumferentially oppositeeach other (i.e., 180 degrees apart). FIG. 12C depicts the grooves inwhich each of the inner electrodes and/or wires may be retained, some ofwhich are also depicted in FIG. 12B. The return wire 1207 may beconnected to the outer electrode sheaths 1206, 1256 in any of theconfigurations described above and may be retained in groove G3. Thewire 1203 connects the first inner electrode 1202 of the first electrodeassembly with the first voltage output VO1, and may be retained ingroove G2. The wire 1205 connects the second inner electrode 1204 of thefirst electrode assembly with the second voltage output VO2, and may beretained in groove G5, directly opposite groove G2. The wire 1253connects the first inner electrode 1252 of the second electrode assemblywith the fourth voltage output VO4, and may be retained in groove G1.The wire 1255 connects the second inner electrode 1254 of the secondelectrode assembly with the fifth voltage output VO5, and may beretained in groove G3, directly opposite groove G1. While the exampledepicted here uses grooves G1-G5, it should be understood that any fiveof the six grooves may be used to retain the wires to attain theconnectivity depicted in FIG. 12A. For example, the wires 1203, 1205,1253, 1255 and 1207 may be retained in grooves G1, G4, G2, G5, G3respectively, or grooves G5, G3, G1, G4, G5 respectively, etc. Asdepicted in FIG. 12B, the circumferential locations of the innerelectrodes of the first electrode assembly are different from thecircumferential locations of the inner electrodes of the secondelectrode assembly, i.e., they are offset from each other by an angle,which angle may be any value of about 1 degree to about 179 degrees,e.g., about 60 degrees, as determined by the location of the groove inwhich the inner electrode is retained. However, in other variations, theinner electrode may span a circumferential length of the catheter (suchas described and depicted in FIG. 6H), which may allow for the electrodeassemblies to be rotated such that shockwaves may be generated from adesired circumferential location. In such variations, the orientation ofthe first and second electrode assemblies may be the same (i.e.,shockwaves may be generated from the same circumferential locationaround the catheter, but longitudinally offset by the distance betweenthe electrode assemblies).

Alternatively or additionally, two electrode assemblies may be connectedin series with respect to each other such that activating a firstelectrode assembly also activates a second electrode assembly. In somevariations, it may be desirable to have multiple shockwave sourceswithout as many wires running along the elongate member, and using fewerports on the voltage pulse generator. For example, connecting twoelectrode assemblies in series may allow the shockwave device tosimultaneously generate up to four different shockwaves using just twovoltage output ports (e.g., one positive channel and one negativechannel). In addition, reducing the number of wires that extend alongthe length of the elongate member would allow the elongate member tobend and flex more freely as it is advanced through the vasculature of apatient (e.g., may allow for a tighter turning radius). One example of aseries connection between two electrode assemblies 1300, 1350 isdepicted in FIGS. 13A-13D. As schematically depicted in FIG. 13A, afirst wire 1303 may connect the first inner electrode 1302 of the firstelectrode assembly to a first voltage output port VO1 of a pulsegenerator 1301. A second wire 1305 (e.g., an interconnect wire) mayconnect the second inner electrode 1304 of the first electrode assembly1300 to a first inner electrode 1352 of the second electrode assembly1350. A third wire 1307 may connect the second inner electrode 1354 to asecond voltage output port VO2 (a ground channel or negative terminal).In some variations, the first voltage output port VO1 may be a positivechannel while the second voltage output port VO2 may be a negativechannel (or vice versa). During a high voltage pulse on the firstvoltage output port VO1, current may flow in the direction of the arrowin the first wire 1303 from the voltage output VO1 to the first innerelectrode 1302 of the first electrode assembly 1200. The high voltagepulse generator may apply a voltage pulse on output port VO1 such thatthe potential difference between the first inner electrode 1302 and theouter electrode 1306 of the first electrode assembly 1300 is high enoughto form a plasma arc between them, generating a bubble that gives riseto a shockwave. The current that traverses the bubble from the firstinner electrode 1302 to the outer electrode 1306 may set up a potentialdifference between the outer electrode 1306 and the second innerelectrode 1304 that is high enough to form a plasma arc between them,generating a bubble that gives rise to a different shockwave (i.e., asecond shockwave). In a variation where the first inner electrode andsecond inner electrode are located circumferentially opposite to eachother (e.g., 180 degrees apart from each other around the circumferenceof the elongate member), the shockwaves generated by the first andsecond inner electrodes may propagate in opposite directions, extendingoutward from the side of the elongate member. The current then flows inthe second wire 1305 to the first inner electrode 1352 of the secondelectrode assembly 1350 and may set up a potential difference betweenthe first inner electrode 1352 and the outer electrode 1356 that is highenough to form a plasma arc between them, generating a bubble that givesrise to another shockwave (i.e., a third shockwave). The current thattraverses the bubble from the first inner electrode 1352 to the outerelectrode 1356 may set up a potential difference between the outerelectrode 1356 and the second inner electrode 1354 of the secondelectrode assembly 1350 that is high enough to form a plasma arc betweenthem, generating a bubble that gives rise to an additional shockwave(i.e., a fourth shockwave). The current then returns to the voltagesource generator via wire 1307 to voltage output port VO2 (which may bea negative channel or a ground channel). Optionally, a connector (notshown) may be provided between the wires 1303, 1307 and the voltagepulse generator 1301 so that the wires of the elongate member may beeasily connected to the output ports of the high voltage generator.

FIGS. 13B-13D depict one variation of how the circuit of FIG. 13A may beimplemented in a shockwave device that comprises the first shockwaveelectrode assembly 1300 and the second shockwave electrode assembly1350. The shockwave device may comprise a catheter 1310 with a centralguide wire lumen 1311 and six longitudinal grooves (G1-G6) arrangedaround the guide wire lumen. FIG. 13B is a top view of the first andsecond electrode assemblies 1300, 1350 where the first inner electrode1302 of the first electrode assembly 1300 and the second inner electrode1354 of the second electrode assembly 1352 are visible. FIG. 13C abottom view of the first and second electrode assemblies 1300, 1350where the second inner electrode 1304 of the first electrode assembly1300 and the first inner electrode 1356 of the second electrode assembly1352 are visible. The first and second inner electrodes of eachelectrode assembly are located circumferentially opposite each other(i.e., 180 degrees apart). FIG. 11D depicts the grooves in which each ofthe inner electrodes and/or wires may be retained. The wire 1303connects the first inner electrode 1302 with the first voltage outputVO1, and may be retained in a proximal length of groove G4 (i.e., thelength of the longitudinal groove that is proximal to the firstelectrode assembly). The wire 1305 connects the second inner electrode1304 of the first electrode assembly with the first inner electrode 1352of the second electrode assembly and may be retained in groove G1,directly opposite groove G4. The wire 1307 connects the second electrode1354 of the second electrode assembly with the second voltage outputVO2, and may be retained in a distal length of groove G4 (i.e., thelength of the longitudinal groove that is distal to the second electrodeassembly). In some variations, the wire 1307 does not directly connectto the second voltage output port VO2, but instead connects with anadditional electrode (e.g., an outer electrode sheath), which is thenconnected by an additional wire to the second voltage output port. Whilethe example depicted here uses grooves G1, G4, it should be understoodthat any two of the six grooves may be used to retain the wires 1303,1305, 1307 to attain the connectivity depicted in FIG. 13A. For example,the wires 1303, 1305, 1307 may be retained in grooves G2 and G5respectively, or grooves G3 and G6 respectively, etc.

Some variations of shockwave devices comprise a plurality of electrodeassemblies, where some of the electrode assemblies are connected inseries, while other electrode assemblies are configured such that thefirst inner electrode and the second inner electrode are eachindependently voltage-controlled (e.g., each connected to separate portson a high voltage pulse generator in a direct connect configuration).This may allow for more shockwaves to be simultaneously generated usingfewer wires than if all the electrode assemblies were connected toseparate voltage channels. Reducing the number of wires along thelongitudinal length of the elongate member may help to maintain theability of the elongate member to bend and flex (e.g., to navigatethrough tortuous vasculature). This may help the elongate member to havea tighter turning radius, and/or to be able to attain a smaller radiusof curvature. An increased number of wires along the length of theelongate member may stiffen the elongate member such that it is nolonger able to navigate tortuous vasculature. In some variations, theshockwave force that is generated from electrode assemblies that areconnected to a plurality of high voltage channels (e.g., where eachinner electrode is connected to a separate voltage channel in a directconnect configuration) may be greater than the shockwave force that isgenerated from electrode assemblies that are configured in series. Insome variations, the voltage applied to electrode assemblies connectedin series needs to be greater than the voltage applied to electrodeassemblies where each inner electrode is directly connected to aseparate voltage channel in order to attain a shockwave of similarmagnitude. In some variations, the voltage pulse applied to electrodesin a series configuration may be longer than the voltage pulse appliedto electrodes in a direct connect configuration in order to generateshockwaves of similar magnitude. A shockwave device that has acombination of electrode assemblies in both series and direct connectcircuit configurations may provide the ability to apply a strongershockwave when desired, but also have the ability to simultaneouslyapply many shockwaves without substantially compromising the flexibilityand turning capability of the catheter by minimizing the number ofwires.

Some shockwave devices may have at least one electrode assemblyconfigured such that its two inner electrodes are connected to separatehigh voltage channels (i.e., a direct connect configuration) and atleast one electrode assembly configured such that its two innerelectrodes are connected in series. In still other variations, ashockwave device may have at least one electrode assembly configuredsuch that its two inner electrodes are connected to separate highvoltage channels and two or more electrode assemblies that are connectedin series. A schematic of a shockwave device that uses both electrodeassemblies that are connected in series and in a direct connectconfiguration is depicted in FIGS. 14A-14G. A shockwave device may havefive electrode assemblies located along its length and an elongatemember (e.g., a catheter with a longitudinal guide wire lumen) with sixgrooves extending along its length. The electrode assemblies may be anyof the electrode assemblies described herein, and may, for example, eachhave a first and second inner electrode, an insulating sheath disposedover the inner electrodes, the insulating sheath having first and secondopenings aligned over the first and second inner electrodes, and anouter electrode sheath disposed over the insulating sheath, the outerelectrode sheath having first and second openings aligned over the firstand second inner openings of the insulating sheath. The openings of theouter electrode may be larger than the openings of the insulatingsheath, and may be coaxially aligned with the openings of the insulatingsheath such that the center of the openings are aligned along the sameaxis. The first and second electrode assemblies 1400, 1420 may beconnected in series and controlled together as a pair, and the fourthand fifth electrode assemblies 1440, 1450 may be connected in series andcontrolled together as a pair, separately from the first and secondelectrodes. The series connections may be similar to the connectiondescribed and depicted in FIGS. 13A-13D. The inner electrodes of thethird electrode assembly (which may be located in between the two pairsof series connected electrode assemblies, with the first and secondelectrode assemblies on one side and the fourth and fifth electrodeassemblies on the other side) may be connected in a direct connectconfiguration, similar to the connected described and depicted in FIGS.10A-10D. The series connections between the first electrode assembly1400 and the second electrode assembly 1420 may comprise a first wire1403 connecting a first voltage output port VO1 to the first innerelectrode 1402 of the first electrode assembly 1400, a second wire 1405(e.g., an interconnect wire) connecting the second inner electrode 1404of the first electrode assembly to the first inner electrode 1422 of thesecond electrode assembly 1420, and a third wire 1407 connecting thesecond inner electrode 1424 of the second electrode assembly to avoltage output port VO5. The third wire 1407 may be part of the currentreturn path to the voltage pulse generator. The series connectionsbetween the fourth electrode assembly 1440 and the fifth electrodeassembly 1450 may comprise a sixth wire 1413 connecting a fourth voltageoutput port VO4 to the first inner electrode 1442 of the fourthelectrode assembly 1440, a seventh wire 1415 (e.g., an interconnectwire) connecting the second inner electrode 1444 of the fourth electrodeassembly to the first inner electrode 1452 of the fifth electrodeassembly 1450, and the third wire 1407 connecting the second innerelectrode 1454 of the fifth electrode assembly to the voltage outputport VO5. The direct connect configuration of the third electrodeassembly 1430 may comprise a fourth wire 1409 connecting a secondvoltage output port VO2 to the first inner electrode 1432 and a fifthwire 1411 connecting a third voltage output port VO3 to the second innerelectrode 1434. The outer electrode 1436 may be connected to the voltageoutput port VO5 via the wire 1407.

FIGS. 14B-14G depict one variation of how the circuit of FIG. 14A may beimplemented in a shockwave device comprising five shockwave electrodeassemblies 1400, 1420, 1430, 1440, 1450. The shockwave device maycomprise a catheter with a central guide wire lumen and six longitudinalgrooves arranged around the guide wire lumen. FIG. 14B is perspectiveview of the five shockwave assemblies 1400, 1420, 1430, 1440, 1450 alongthe distal portion of the catheter. The shockwave device depicted theremay have a proximal marker band and a distal marker band (e.g., such asangioplasty marker bands). FIG. 14C is a close-up view of the firstshockwave electrode assembly 1400, the second shockwave electrodeassembly 1420, and the third shockwave assembly 1430. As describedabove, the first and second electrode assemblies 1400, 1420 may beconnected in series, where the wires 1403, 1405, 1407 and innerelectrodes 1402, 1404, 1422, 1424 are retained within two of the sixgrooves, and may for example, be similar to the configuration depictedin FIGS. 13B-13D. Applying a high voltage pulse on wire 1403 maygenerate four radial shockwaves propagating from circumferentiallyopposite sides of the catheter. Two of the shockwaves may originate at alongitudinal location along the catheter corresponding to the locationof the first electrode assembly 1400 and the other two shockwaves mayoriginate at a longitudinal location along the catheter corresponding tothe location of the second electrode assembly 1420. FIG. 14D is aclose-up view of the fourth shockwave electrode assembly 1440, the fifthshockwave electrode assembly 1450, and a distal radiopaque marker band1460. As described above, the fourth and fifth electrode assemblies1440, 1450 may be connected in series, where the wires 1413, 1415, 1407and inner electrodes 1442, 1444, 1452, 1454 are retained within two ofthe six grooves, and may for example, be similar to the configurationdepicted in FIGS. 13B-13D. In some variations, the wires and innerelectrodes may be in a pair of grooves that are different from the pairof grooves retaining the wires and inner electrodes of the first andsecond electrode assemblies. Applying a high voltage pulse on wire 1413may generate four radial shockwaves propagating from circumferentiallyopposite sides of the catheter. Two of the shockwaves may originate at alongitudinal location along the catheter corresponding to the locationof the fourth electrode assembly 1440 and the other two shockwaves mayoriginate at a longitudinal location along the catheter corresponding tothe location of the fifth electrode assembly 1450.

FIG. 14E is a close-up view of the fifth electrode assembly 1450 and thedistal marker band 1460. In some variations of shockwave devices, thewire connected to the second inner electrode 1454 of the fifth electrodeassembly 1450 may be connected to the distal marker band 1460. Thedistal marker band 1460 may act as a common node for wires that carrythe return currents from the electrode assemblies, which may help reducethe number of wires carrying a return current back to the high voltagepulse generator. There may be several of such return path nodes alongthe length of the catheter, and may be, for example, one or moreadditional radiopaque marker bands, and/or one or more outer electrodesheaths of certain electrode assemblies.

FIG. 14F is a close-up view of the third electrode assembly 1430. Asdescribed above, the inner electrode 1432 and inner electrode 1434(which is not visible in this view) may be in a direct connectconfiguration such that they may be individually driven by separateoutputs from the voltage generator. The currents from the innerelectrodes may flow to the outer electrode 1436, which may return thecurrent to the high voltage pulse generator via the third wire 1407.Alternatively, or additionally, the current from the outer electrode1436 may return to the high voltage pulse generator via an eighth wire1461. The eighth wire 1461 may be retained in a groove that is oppositethe groove that retains the third wire 1407. FIG. 14G depicts the wires1409, 1411, 1461 retained within three grooves of the catheter, wherethe wires 1409, 1411 are connected to the inner electrodes 1432, 1434,and retained in grooves that are opposite to each other. The wire 1461may contact the outer electrode 1436 and may be retained in a thirdgroove (similar to the configuration described and depicted in FIGS.10A-10D).

While FIGS. 14A-14F depict a shockwave device with five electrodeassemblies located along the length of the elongate member, it should beunderstood that a shockwave device may have any number of electrodeassemblies connected in any combination of series and direct connectconfigurations. For example, a shockwave device may have two electrodeassemblies that are connected to each other in series, which may allowfor the synchronized generation of four different shockwavessimultaneously. Alternatively, a shockwave device may have two electrodeassemblies where the two inner electrodes of each assembly are eachconnected to separate high voltage channels in a direct connectconfiguration, which may allow for the independent generation of fourdifferent shockwaves, either simultaneously or sequentially. The numberof electrode assemblies along the length of the elongate member of ashockwave device may be selected according to the geometry of the targettissue region. For example, a shockwave device intended for breaking upcalcified plaques along a long vessel segment may have five electrodeassemblies along its length, while a device for breaking up plaques in ashorter vessel segment may have two electrode assemblies along itslength.

Any of the shockwave assemblies described herein may be used in anangioplasty procedure for breaking up calcified plaques accumulatedalong the walls of a vessel. One variation of a method may compriseadvancing a guide wire from an entry site on a patient (e.g., an arteryin the groin area of the leg) to the target region of a vessel (e.g., aregion having calcified plaques that need to be broken up). A shockwavedevice comprising a catheter with a guide wire lumen, one or morelow-profile electrode assemblies located along a length of the catheter,and a balloon may be advanced over the guide wire to the target regionof the vessel. The shockwave electrode assemblies may be any of thelow-profile electrode assemblies described herein. The balloon may becollapsed over the catheter while the device is advanced through thevasculature. The location of the shockwave device may be determined byx-ray imaging and/or fluoroscopy. When the shockwave device reaches thetarget region, the balloon may be inflated by a fluid (e.g., salineand/or saline mixed with an image contrast agent). The one or moreelectrode assemblies may then be activated to generate shockwaves tobreak up the calcified plaques. The progress of the plaque break-up maybe monitored by x-ray and/or fluoroscopy. The shockwave device may bemoved along the length of the vessel if the calcified region is longerthan the length of the catheter with the electrode assemblies, and/or ifthe calcified region is too far away from the electrode assemblies toreceive the full force of the generated shockwaves. For example, theshockwave device may be stepped along the length of a calcified vesselregion to sequentially break up the plaque. The electrode assemblies ofthe shockwave device may be connected in series and/or may be connectedsuch that each inner electrode is connected to separate high voltagechannels, and may be activated simultaneously and/or sequentially, asdescribed above. For example, a pair of electrode assemblies may beconnected in series and activated simultaneously, while anotherelectrode assembly may be connected such that each inner electrode isconnected to separate high voltage channels, and activated sequentiallyand/or simultaneously. Once the calcified region has been sufficientlytreated, the balloon may be inflated further or deflated, and theshockwave device and guide wire may be withdrawn from the patient.

It will be understood that the foregoing is only illustrative of theprinciples of the invention, and that various modifications, alterationsand combinations can be made by those skilled in the art withoutdeparting from the scope and spirit of the invention. Any of thevariations of the various shockwave devices disclosed herein can includefeatures described by any other shockwave devices or combination ofshockwave devices herein. Furthermore, any of the methods can be usedwith any of the shockwave devices disclosed. Accordingly, it is notintended that the invention be limited, except as by the appendedclaims. For all of the variations described above, the steps of themethods need not be performed sequentially.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A device for generating shockwaves comprising:an axially extending catheter; a balloon surrounding a portion of thecatheter, said balloon being fillable with a conductive fluid; aninsulating layer wrapped around a portion of the catheter within theballoon, said layer having a first aperture therein; a first innerelectrode carried within the catheter and aligned with the firstaperture of the insulating layer; and an outer electrode mounted on theinsulating layer and having a first aperture coaxially aligned with thefirst aperture in the insulating layer and arranged so that when theballoon is filled with fluid and a voltage is applied across theelectrodes, a first shockwave will be initiated from a first sidelocation of the catheter.
 2. A device as recited in claim 1, whereinsaid insulating layer is an insulating sheath and said outer electrodeis in the form of a sheath that is circumferentially mounted around theinsulating sheath.
 3. A device as recited in claim 1, wherein the sizeof the first aperture in the outer electrode is larger than the size ofthe first aperture in the insulating sheath.
 4. The device of claim 1,further comprising a first wire, and a second wire, wherein the firstand second wires extend along the length of the catheter, and whereinthe first wire is connected to the first inner electrode, and the secondwire is connected to the outer electrode.
 5. The device of claim 4,wherein the catheter has first and second grooves that extend along thelength of the catheter, and the first wire is slidably disposed withinthe first groove and the second wire is slidably disposed within thesecond groove.
 6. The device of claim 4, wherein the first innerelectrode and the outer electrode are crimped over an electricallyconductive portion of the first and second wires, respectively.
 7. Thedevice of claim 6, wherein the first inner electrode is a hypotube thatis crimped over the first wire.
 8. A device as recited in claim 2,wherein: the insulating sheath has a second aperture circumferentiallyopposite the first aperture in the insulating sheath; the device furthercomprises a second inner electrode aligned with the second aperture inthe insulating sheath; and the outer electrode sheath has a secondaperture coaxially aligned with the second aperture in the insulatingsheath and arranged so that when the balloon is filled with a fluid anda voltage is applied across the second inner electrode and the outerelectrode, a second shockwave will be initiated from a second sidelocation of the catheter that is opposite to the first side location. 9.The device of claim 8, further comprising a first wire, a second wire,and a third wire, wherein the first, second and third wires extend alongthe length of the catheter, and wherein the first wire is connected tothe first inner electrode, the second wire is connected to the outerelectrode, and the third wire is connected to the second innerelectrode.
 10. The device of claim 9, wherein the catheter has first,second and third grooves that extend along the length of the catheter,and the first wire is slidably disposed within the first groove, thesecond wire is slidably disposed within the second groove, and the thirdwire is slidably disposed within the third groove.
 11. The device ofclaim 9, wherein the first inner electrode and the second innerelectrode are crimped over an electrically conductive portion of thefirst and third wires, respectively.
 12. The device of claim 11, whereinthe first inner electrode and the second inner electrode are first andsecond hypotubes that are each crimped over the first and third wires,respectively.
 13. The device of claim 12, wherein the surface of thefirst and second crimped hypotubes each circumferentially spans aportion of the elongate member.
 14. The device of claim 13, wherein thefirst and second crimped hypotubes each circumferentially span at least⅙ of the way around the circumference of the elongate member.
 15. Adevice as recited in claim 8, wherein: the insulating sheath has a thirdaperture circumferentially 90 degrees from the first aperture in theinsulating sheath; the device further comprises a third inner electrodealigned with the third aperture in the insulating sheath; and the outerelectrode sheath has a third aperture coaxially aligned with the thirdaperture in the insulating sheath and arranged so that when the balloonis filled with a fluid and a voltage is applied across the third innerelectrode and the outer electrode, a third shockwave will be initiatedfrom a third side location that is 90 degrees offset from the first sidelocation.
 16. A device as recited in claim 15, wherein: the insulatingsheath has a fourth aperture circumferentially opposite the thirdaperture in the insulating sheath; the device further comprises a fourthinner electrode aligned with the fourth aperture in the insulatingsheath; and the outer electrode sheath has a fourth aperture coaxiallyaligned with the fourth aperture in the insulating sheath and arrangedso that when the balloon is filled with a fluid and a voltage is appliedacross the fourth inner electrode and the outer electrode, a fourthshockwave will be initiated from a fourth side location that is oppositeto the third side location.
 17. A device for generating shockwavescomprising: an axially extending catheter; a balloon surrounding aportion of the catheter, said balloon being fillable with a conductivefluid; a first inner electrode mounted on the side of the catheter; aninsulating layer having an aperture disposed over the first innerelectrode such that the aperture is coaxially aligned with the firstinner electrode; and an outer electrode having an aperture disposed overinsulating layer such that the outer electrode aperture is coaxiallyaligned with the insulating layer aperture.
 18. The device of claim 17,wherein the first inner electrode, insulating layer and outer electrodedo not protrude more than 0.015 inch from the outer surface of thecatheter.
 19. The device of claim 17, further comprising a second innerelectrode mounted on the side of the catheter at a location that iscircumferentially opposite to the first inner electrode, and wherein theinsulating layer has a second aperture coaxially aligned with the secondinner electrode and the outer electrode has a second aperture that iscoaxially aligned with the second aperture of the insulating layer. 20.A system for generating shockwaves comprising: an axially extendingcatheter; a balloon surrounding a portion of the catheter, said balloonbeing fillable with a conductive fluid; a first electrode assembly at afirst location along the length of the catheter, the first electrodeassembly comprising a first inner electrode, a second inner electrode,and an outer electrode and configured to initiate shockwaves at twocircumferentially opposite locations; a second electrode assembly at asecond location along the length of the catheter, the second electrodeassembly comprising a first inner electrode, a second inner electrode,and an outer electrode and configured to initiate shockwaves at twocircumferentially opposite locations; a third electrode assembly at athird location along the length of the catheter, the third electrodeassembly comprising a first inner electrode, a second inner electrode,and an outer electrode and configured to initiate shockwaves at twocircumferentially opposite locations; a fourth electrode assembly at afourth location along the length of the catheter, the fourth electrodeassembly comprising a first inner electrode, a second inner electrode,and an outer electrode and configured to initiate shockwaves at twocircumferentially opposite locations; a fifth electrode assembly at afifth location along the length of the catheter, the fifth electrodeassembly comprising a first inner electrode, a second inner electrode,and an outer electrode and configured to initiate shockwaves at twocircumferentially opposite locations; and a voltage pulse generator,wherein the channels of the voltage pulse generator are connected to oneor more of the electrode assemblies.
 21. The device of claim 20,wherein: the first inner electrode of the first electrode assembly isconnected is a first output of the voltage pulse generator, the secondinner electrode of the first electrode assembly is connected to thefirst inner electrode of the second electrode assembly, the first innerelectrode of the third electrode assembly is connected to a secondoutput of the voltage pulse generator, the second inner electrode of thethird electrode assembly is connected to a third output of the voltagepulse generator, the first inner electrode of the fourth electrodeassembly is connected to a fourth output of the voltage pulse generator,the second inner electrode of the fourth electrode assembly is connectedto the first inner electrode of the fifth electrode assembly, and thesecond inner electrode of the second electrode assembly, the outerelectrode of the third electrode assembly, and the second innerelectrode of the fifth electrode assembly are all connected to a fifthoutput of the voltage pulse generator.
 22. A device for generatingshockwaves comprising: an elongate member; a first electrode assemblylocated along the side of the elongate member at a first longitudinallocation, wherein the first electrode assembly is configured to initiateshockwaves at a first side location on the elongate member; a secondelectrode assembly circumferentially opposite the first electrodeassembly, wherein the second electrode assembly is configured toinitiate shockwaves at a second side location that is circumferentiallyopposite the first side location of the elongate member; and a balloonsurrounding a portion of the elongate member, the balloon being fillablewith a conductive fluid.
 23. A system for generating shockwavescomprising: a high voltage pulse generator having a plurality of highvoltage output channels; a catheter; a plurality of shockwave sourceslocated along a length of the catheter, wherein the number of highvoltage output channels driving the plurality of shockwave sources isless than the number of shockwave sources; and a balloon surrounding thelength of the catheter that has the shockwave sources, the balloon beingfillable with a conductive fluid.